Length-dependent potentiation and myosin light chain phosphorylation in rat gastrocnemius muscle.

@article{Rassier1997LengthdependentPA,
  title={Length-dependent potentiation and myosin light chain phosphorylation in rat gastrocnemius muscle.},
  author={Dilson E. Rassier and L. Aaron Tubman and Brian R MacIntosh},
  journal={The American journal of physiology},
  year={1997},
  volume={273 1 Pt 1},
  pages={
          C198-204
        }
}
Changes in muscle length affect the degree of staircase potentiation in skeletal muscle, but the mechanism by which this occurs is unknown. In this study, we tested the hypothesis that length-dependent change in staircase is modulated by phosphorylation of the myosin regulatory light chains (RLC), since this is believed to be the main mechanism of potentiation. In situ isometric contractile responses of rat gastrocnemius muscle during 10 s of repetitive stimulation at 10 Hz were analyzed at… 
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It is indicated that length dependence of potentiation in intact skeletal muscle is abolished by lowering the pH, and the mechanism of length-dependent potentiation may be closely related to thelength dependence of Ca(2+) sensitivity, and changes in the charge potential of the myofilaments may be important in regulating this relationship.
Length dependence of staircase potentiation: interactions with caffeine and dantrolene sodium.
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It is confirmed that there is a length dependence of staircase potentiation in mammalian skeletal muscle which is suppressed by caffeine and dantrolene sodium, which is apparently not directly modulated by Ca2+ availability in the myoplasm.
Sarcomere length-dependence of activity-dependent twitch potentiation in mouse skeletal muscle
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There is no evidence that posttetanic potentiation is fundamentally different from staircase in these muscles, and the relative magnitude of the twitch contraction (Pt)*Pt was proportional to sarcomere length with a negative slope, over the range 2.3 μm – 3.7 μm.
Caffeine and length dependence of staircase potentiation in skeletal muscle.
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It is shown that length dependence of Ca2+ sensitivity in intact skeletal muscle is diminished by caffeine, suggesting that the mechanism of this length dependence may be closely related to the mechanism for length dependence for Ca2+, which is greater at long lengths.
Cellular and whole muscle studies of activity dependent potentiation.
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TLDR
Activity dependent potentiation is an important functional modulator of contractile response and is used to describe the progressive increase in amplitude of contraction with sequential twitches or incompletely fused tetanic contractions.
Myosin phosphorylation and force potentiation in skeletal muscle: evidence from animal models
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Recent work from a variety of muscle models indicates the presence of a secondary mechanism for potentiation that may involve altered Ca2+ handling, an effect that may translate to enhanced physiological function in vivo.
Potentiation of shortening and velocity of shortening during repeated isotonic tetanic contractions in mammalian skeletal muscle
TLDR
The slower rate of change in shortening and velocity may be due to approaching maximal velocity for this short duration of contraction, but is not due to slowing of the rate of phosphorylation of the myosin regulatory light chains.
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Inhibition of Ca2+ release alters summation, but repetitive stimulation leading to fatigue changes it more substantially.
Length-dependent twitch contractile characteristics of skeletal muscle.
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Observations suggest that double-pulse contractions are more suitable for setting length for experimental studies than twitch contractions, but the mechanisms of this change in time course remain unclear.
Potentiation of isometric and isotonic contractions during high-frequency stimulation
TLDR
The observations indicate the possibility that activity dependent potentiation can result in significant improvement in both isometric and dynamic contractions, even when activated at very high frequency.
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References

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